The present invention relates, in general, to the layout and use of a plurality of low-pressure permanent mold (LPPM) casting machines, and more specifically to deployment of modified LPPM casting machines on a rotary table.
It is known to use a low pressure countergravity casting apparatus to cast molten metal into a mold. One example of such an apparatus is described in U.S. Pat. No. 5,215,141, which is incorporated herein by reference. Basically, in a low pressure countergravity casting apparatus, metal (e.g., aluminum) is melted in a melt furnace and then supplied to a holding furnace. The holding furnace includes a supply conduit for introducing a gas under pressure into the holding furnace. As the gas is introduced, the molten metal is forced through a submerged feed tube into the mold. The feed tube is commonly referred to as a stalk tube. The mold receives the molten metal through holes in the bottom of the mold.
The holding furnace located beneath the mold in a prior art LPPM casting machine has been constructed to operate in a fixed location near a supply of molten metal. A human operator monitors machine operation, such as removing cast parts and operating molten metal refill equipment. Due to the structure and operation of prior art LPPM machines, one human operator could tend at most two or perhaps three machines simultaneously. It would be desirable to reduce the manufacturing floor space required for LPPM machines and to reduce the need for human operators.
The present invention has the advantage of successfully molding articles in low pressure permanent mold casting machines while reducing floor space, capital expense, and labor costs.
In one preferred aspect of the invention, apparatus for making a cast article comprises a rotary table with a drive for indexing the rotary table to a plurality of rotational positions. Molten metal supply apparatus is placed at a first fixed location adjacent to said rotary table. A plurality of casting machines are supported at predetermined spacings on the rotary table, each respective casting machine having a respective holding furnace feeding a respective stalk tube and having a molten metal inlet port for receiving molten metal from the molten metal supply apparatus when the respective casting machine is indexed to a fill position adjacent the first fixed location. Each respective casting machine is adapted to receive a mold and having an open mold configuration and a closed mold configuration. A cast article removal apparatus is placed at a second fixed location adjacent the rotary table for removing the cast article from a respective casting machine when the respective casting machine is at an unload position adjacent the second fixed location and is in the open mold configuration.
Further advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.